1. Field of the Invention
This invention relates to seismic energy dissipation using damping apparatus. More particularly, this invention relates to an apparatus, method, and system for absorbing and dissipating seismic energy manifest by relative movement between two members in a structure, such as a building. The systemic embodiment of this invention in a building includes plural seismic dampers and rigid shear panel members distributed or arrayed in the building so that seismic energy is absorbed and dissipated in a distributed arrangement throughout the building structure which both avoids stress concentrations in the building structure, and dissipates a greater amount of seismic energy than conventionally would be possible using concentrated damping instruments.
2. Related Technology
Seismic energy dissipation using damping devices is well known. For example, a technical paper entitled, Seismic Response Evaluation of Post-Tensioned Precast Concrete Frames With Friction Dampers, presented at the Proceedings of the 8th U.S. National Conference on Earthquake Engineering, Apr. 18-22, 2006, San Francisco, Calif., USA. This paper discusses the seismic response evaluation of unbonded post-tensioned precast concrete moment frames with friction dampers at the beam ends. Another type of friction damper is illustrated in a report to the National Science Foundation, entitled, “Slotted Bolted Connection Energy Dissipaters (with April 1993 Addendum of some recent results), published in Steel Tips, by the Structural Steel Engineering Council, Technical Information & Product Service, Report No. UCB/EERC-92/10, July 1992. Slotted bolted connections (SBC's) of two types are evaluated for their ability to dissipate energy through friction. One SBC is steel-on-steel, and the other is steel-on-brass.
Further to the above, it is known to provide diagonal braces, either in original construction or as part of a seismic retrofit program, to brace a building having an otherwise open rectangular frame or beam structure. These diagonal braces assist in stiffening the building structure against shear forces resulting from lateral seismic ground motions, and reduce the amplitude of the displacements the building experiences in response to these shear forces. As a result, damage to the building during a seismic event is reduced, and the building will better withstand a higher level of earthquake while cost-effective construction is obtained.
U.S. Pat. No. 5,560,162 illustrates a variation of this diagonal bracing concept, in which the diagonal bracing is accompanied by a so-called seismic brake. The seismic brake includes a cylindrical member or pipe gripped by a gripping block. The gripping strength of the gripping block on the pipe is adjustable, so that below a certain force level, the diagonal brace acts as a rigid connection. However, if the force level between the pipe and gripping block exceeds the certain force level (i.e., as a result of a seismic event) then the pipe and gripping block move relatively to one another, the diagonal brace temporarily becomes flexible (with Coulomb damping), and seismic energy is frictionally dissipated in the seismic brake. Upon the conclusion of the seismic event, the gripping block again grips the pipe immovably, and the diagonal brace is again rigid.
However, the amount of seismic energy which can be dissipated by the seismic brake of the '162 patent is inherently limited by the comparatively small size and extent of the brake defined between the pipe and gripping block. Also, the energy dissipation is concentrated at the gripping block and pipe, so that stress concentrations within the building structure can result. Still further, the structure of the seismic brake is rather expensive, so that building owners are hesitant to install a sufficient number of these devices to deal with predicted seismic forces.